Known carpal tunnel knives have a handle with a blade holder. The blade holder has two finger-like prongs extending forwardly above and below the blade. An example of this type of surgical knife is found in U.S. Pat. No. 5,387,222 issued to Strickland.
The prongs extend beyond the blade and straddle the targeted tissue to be cut. The prongs assist in guiding the blade only through the targeted carpal ligament during carpal tunnel release surgery. One prong may be longer than the other, with the longer prong guided below the carpal ligament in an attempt to protect the median nerve and other tissues from unwanted damage.
The surgical blade is positioned between the two prongs and is wide enough to cut the entire thickness of the targeted tissue, but not endanger surrounding tissue. A common width is 3 mm, which roughly corresponds to the thickness of most adults' carpal tunnel ligaments.
However, with the known carpal tunnel knives inserted into the patient's hand, it is still difficult to locate the exact position of the instrument and its cutting blade. Surgeons must still locate the instrument in the patient's hand by feel, mainly by the resistance experienced by the cutting blade and the distance the knife is inserted into the patient's hand. While the knife is inserted, it obstructs light entry into the surgical wound thus interfering with the surgeons ability to see the surgical site.